One look and you'll notice it immediately: beautiful floral patterns, resembling white stencil tracings, seem etched on the outer surface of this piece of seaweed. It looks so out of place, you'd swear it was artificial. What is it? We've found the answer.

The thread soon erupted with responses, but one quickly worked its way to the top. According to redditor Brrrtje, the seaweed is "is carrying a colony of Botryllus schlosseri," a small marine invertebrate commonly found clinging to slow-moving objects in cold, saltwater environments.

A little digging reveals that Brrrtje is spot on. B. schlosseri, also known as "star tunicates" are very distinctive looking, and are readily distinguished from other Botrylloides by the unmistakable floral pattern that they form in the presence of other members of their species. Stanford researchers Heather Boyd, Irving Weissman and Yasunori Saito describe the peculiar organism in a June, 1990 issue of The Biological Bulletin:

A colony [Fig. 1a, pictured here] is composed of many zooids called blastozooids [a zooid is a single animal in a group of colonial organisms], which are arranged in oval or star-shaped systems. These systems are connected to one another, as are the zooids within any system itself, by a common vascular network... Each system is composed fo 5—15 blastozooids, which share a common cloacal aperture in the center of the system.